When the sun rises on December 22, as it surely will, do not
expect apologies or even a rethink. No matter how often apocalyptic
predictions fail to come true, another one soon arrives. And the
prophets of apocalypse always draw a following-from the 100,000
Millerites who took to the hills in 1843, awaiting the end of the
world, to the thousands who believed in Harold Camping, the
Christian radio broadcaster who forecast the final rapture in both
1994 and 2011.

Predictions of global famine and the end of oil in the 1970s
proved just as wrong as end-of-the-world forecasts from
millennialist priests. Yet there is no sign that experts are
becoming more cautious about apocalyptic promises. If anything, the
rhetoric has ramped up in recent years. Echoing the Mayan calendar
folk, theBulletin of the Atomic Scientists moved its Doomsday Clock one minute closer to
midnight at the start of 2012, commenting: "The global community
may be near a point of no return in efforts to prevent catastrophe
from changes in Earth's atmosphere."

Over the five decades since the success of Rachel
Carson's Silent Spring in 1962 and the four decades since
the success of the Club of Rome's The Limits to Growth in
1972, prophecies of doom on a colossal scale have become routine.
Indeed, we seem to crave ever-more-frightening predictions-we are
now, in writer Gary Alexander's word, apocaholic. The past half century has
brought us warnings of population explosions, global famines,
plagues, water wars, oil exhaustion, mineral shortages, falling
sperm counts, thinning ozone, acidifying rain, nuclear winters, Y2K
bugs, mad cow epidemics, killer bees, sex-change fish,
cell-phone-induced brain-cancer epidemics, and climate
catastrophes.

So did we or didn't we? Last week saw the publication of two new
papers with diametrically opposed conclusions about whether
non-African people have Neanderthal-human hybrids among their
ancestors-a result of at least some interspecies dalliance in the
distant past.

That non-Africans share 1% to 4% of their genomes with
Neanderthals is not in doubt, thanks to the pioneering work of
paleo-geneticists led by the Max Planck Institute's Svante Paabo.
At issue is how to interpret that fact. Dr. Paabo originally
recognized that there are two possible explanations, hybridization
(which got all the press) or "population substructure."

Identifying unique features of human beings is a cottage
industry in psychology. In his book "Stumbling on Happiness," the Harvard
psychologist Daniel Gilbert jokes that every member of his
profession lives under the obligation at some time in his career to
complete a sentence which begins: "The human being is the only
animal that..." Those who have completed the sentence with phrases
like "makes tools," "is conscious" or "can imitate" have generally
now conceded that some other animals also have these traits.

Plenty of human uniqueness remains. After all, uniqueness is
everywhere in the biological world: Elephants and worms also have
unique features. As fast as one scientist demotes human beings from
being unique in one trait, another scientist comes up with a new
unique trait: grandparental care, for instance, or extra spines on
the pyramidal cells of our prefrontal cortex.

My latest Mind and Matter column in the Wall
Street Journal is the third in the series on confirmation bias.

I argued last week that the way to combat confirmation bias-the
tendency to behave like a defense attorney rather than a judge when
assessing a theory in science-is to avoid monopoly. So long as
there are competing scientific centers, some will prick the bubbles
of theory reinforcement in which other scientists live.